Generally, there has been used a method of performing a chromate treatment on a metal material surface by the use of a process liquid having excellent adhesion to a metal material surface and mainly including chromic acid, dichromic acid, or salts thereof, as a technique for providing corrosion resistance, fingerprint resistance, or the like to the metal material surface.
Recently, considering that a chromate treatment film includes a large amount of noxious hexavalent chrome, a surface treatment technique using a non-chrome base usable as a substitute of a chromate film has been developed due to concern about environment. As such a non-chrome based surface treatment technique, for example, there have been known for practical use, a method of applying a treatment using inorganic components, a method of applying a phosphate treatment, a method of applying a treatment using an elementary substance of silane coupling agent, a method of applying a organic resin coating treatment, and the like.
As a technique mainly using inorganic components, for example, in Patent Document 1, there is disclosed a treatment using a metal surface treatment agent containing a vanadium compound; and a metal compound including at least one kind of metal selected from the groups including zirconium, titanium, molybdenum, tungsten, manganese, and cerium.
As a technique mainly using silane coupling agent, for example, in Patent Document 2, there is disclosed a treatment of a metal sheet using an aqueous solution containing an organic functional silane with low concentration and a cross-linking agent, to provide temporary corrosion protection. Also, in Patent Document 2, there is described a method in which the cross-linking agent cross-links the organic functional silane, thereby forming a dense siloxane film.
For example, in Patent Document 3, there is disclosed a method of producing a non-chrome based steel sheet having excellent corrosion resistance and having excellent fingerprint resistance, blackening resistance, and coating adhesion by applying a surface treatment agent containing a specified resin compound (A), a cationic urethane resin (B) having at least one kind of cationic functional group selected from primary to tertiary amino groups and a quaternary ammonium base, one or more kinds of silane coupling agents (C) having a specified reactive functional group, and a specified acid compound (E), in which the contents of the cationic urethane resin (B) and the silane coupling agent (C) fall within predetermined ranges.    [Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2002-30460    [Patent Document 2] U.S. Pat. No. 5,292,549    [Patent Document 3] Japanese Unexamined Patent Application, First Publication No. 2003-105562